Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 18 Jun 2013, 16:24

# The temperature of a certain cup of coffee 10 minutes after

Author Message
TAGS:
Intern
Joined: 16 Apr 2010
Posts: 23
Followers: 0

Kudos [?]: 0 [0], given: 0

The temperature of a certain cup of coffee 10 minutes after [#permalink]  28 Jul 2010, 09:11
00:00

Question Stats:

76% (02:06) correct 23% (02:12) wrong based on 13 sessions
The temperature of a certain cup of coffee 10 minutes after it was poured was 120 degree Fahrenheit . If the temp F of the coffee t minutes after it was poured can be determine by the formula F=120 (2^-at)+60 , where F is degree Fahrenheit and a is constant, then the temperature of the coffee 30 minutes after it was poured was how many degree Fahrenheit

A. 65
B. 75
C. 80
D. 85
E. 90
[Reveal] Spoiler: OA
Manager
Joined: 16 Apr 2010
Posts: 225
Followers: 3

Kudos [?]: 29 [0], given: 12

Re: Problme [#permalink]  28 Jul 2010, 11:57
Hi,

Since F=120 (2^-at)+60,
replace F=120, t=10 to find a.
Once you find a, then to find the temperature 30 min after it was poured simply replace
t=30 and value of a in the equation.

regards,
Jack
VP
Status: The last round
Joined: 18 Jun 2009
Posts: 1325
Concentration: Strategy, General Management
GMAT 1: 680 Q48 V34
Followers: 43

Kudos [?]: 386 [0], given: 156

Re: Problme [#permalink]  28 Jul 2010, 13:26
Is the question correctly written?? I am unable to find the solution.

F= 120* (\frac{1}{2^at}) + 60
Is this formula correct?
_________________
Intern
Joined: 16 Apr 2010
Posts: 23
Followers: 0

Kudos [?]: 0 [0], given: 0

Re: Problme [#permalink]  28 Jul 2010, 13:40
Yes this is how it is written.
GMAT Club team member
Joined: 02 Sep 2009
Posts: 12096
Followers: 1876

Kudos [?]: 10096 [0], given: 959

Re: Problme [#permalink]  29 Jul 2010, 04:03
kilukilam wrote:
The tempreature of a certain cup of coffee 10 minutes after it was poured was 120 degree Faranite. If the temp F of the coffee t minues after it was poured can be determinde by the formula F=120 (2^-at)+60 , where F is degree Fahrenhite and a is constant, then the tempreature of the cofffee 30 minues after it was poured was how many degree fahrenhite

a. 65
b. 75
c. 80
d. 85
e. 90

We have the formula for calculating temperature: F=120*2^{-at}+60 and the value for t=10 --> F(t=10)=120=120*2^{-10a}+60 --> \frac{1}{2^{10a}}=\frac{1}{2} --> 10a=1 --> a=0.1. So formula is F=120*2^{-0.1t}+60

Now for t=30 the temperature in Fahrenheits will be F=120*2^{-0.1*30}+60=\frac{120}{2^3}+60=75.

_________________
Re: Problme   [#permalink] 29 Jul 2010, 04:03
Similar topics Replies Last post
Similar
Topics:
A coffee shop sold 35 cups of coffee. Of these, 15 1 18 Jul 2003, 19:10
The temperature of a certain cup of coffee 10 minutes after 3 24 Apr 2006, 06:38
The temperature of a cup of coffee 10 minutes after it was 7 03 Oct 2006, 17:43
The temperature of a certain cup of coffee 10 minutes after 4 12 Nov 2006, 00:16
The temperature of a certain cup of coffee 10 minutes after 2 12 Aug 2007, 12:45
Display posts from previous: Sort by